Astronomy Picture of the Day

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Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.

2011 September 7

SDSS J102915+172927: A Star That Should Not Exist Image Credit: ESO,
DSS2

Explanation:
Why does this star have so few heavy elements?
Stars born in the
generation of our Sun have an expected abundance of elements heavier than
hydrogen and
helium mixed into their atmospheres.
Stars born in the generation before our Sun,
Population II stars, the stars that created most of the heavy elements
around us today, are seen to have some, although fewer, elements heavier
than H and He.
Furthermore, even the elusive never-seen first stars in the universe, so-called
Population III stars, are predicted to have a large mass and a small but set amount of heavy elements.
Yet low-mass Milky Way star
SDSS J102915+172927, among others, appears to have fewer metals than
ever predicted for any stars, including at least 50 times less lithium
than came out of the Big Bang.
The unusual nature of
this star, initially cataloged by the
Sloan Digital Sky Survey (SDSS) and
pictured above, was
discovered by detailed spectroscopic observations by a large
VLT telescope in
Chile.
Many models of star formation indicate that such a
star
should not even form.
Research is ongoing, however, with one leading hypothesis
holding that fragile primordial
lithium was destroyed in the star's hot core.